The fundus of the eye is the interior surface of the eye behind the lens which includes the retina, optic disc, macula and fovea. The fundus of the eye can be directly examined through an ophthalmoscope by a physician or pictured using a fundus camera. Pupil dilation increases the field of view of the examination system and improves the quality of the image seen or obtained. The image provided may capture a significant area of the retina. Contrast agents and improved digital imaging sensors today provide high quality pan retinal images. A source of light within the ophthalmoscope or a fundus camera further improves tissue illumination and image quality. A wide set of fundus lenses are available and in common practice today in conjunction with illumination and viewing systems.
The human eye is blind to the infrared portion of the electromagnetic spectrum. However, some image sensors which are available today have at least some degree of sensitivity to the infrared spectrum. Light sources within eye fundus visualization systems may also provide some infrared output. U.S. Patent application number 2012/0239015 discloses the use of an illuminating system configured to produce visible and infrared light. Using infrared light during an eye examination has the advantage that the IR light does not create eye dazzling and therefore the patient may be able to keep his or her eyes open during the examination or treatment. This allows a continuous imaging of the eye fundus. Short pulses of visible light periodically provide a more detailed snapshot image of the fundus and may be superimposed on the continuous IR image. The above-mentioned application discloses an ophthalmoscope which is configured to deliver therapeutic laser radiation onto the fundus of the eye while acquiring and presenting real time sequences of images of the retina. Such image sequences may be compared and analyzed for the sake of monitoring a laser treatment.
The quality and magnification of an eye fundus image which is generated by an ophthalmoscope is limited. During conventional examination and treatments, a more precise and detailed picture of the target tissue may be required. A slit lamp, a common implement today, is configured to produce such images. The slit lamp is the most frequently used and most universally applicable instrument among ophthalmologists. The slit lamp is named after its illumination system which intended to produce a “slit” image which is very bright but relatively narrow. The exact distance of the slit image produced from the instrument, as well as the slit's length, width and position are fully variable and controlled by the operator. Kohler illumination optics eliminate the image of the lamp's filament from the field of view. A high luminance halogen lamp is often used to change the color of the tissue to yellow to make it more noticeable. Such color changes have diagnostic importance. A slit lamp microscope may provide a stereoscopic observation and magnification. Fundus lenses may be used in conjunction with a slit lamp to create an image of the fundus.
Typically, the slit lamp and the microscope are generally oriented perpendicular to each other, but share a common focal point and can be mutually rotated about their common focal point. Although using a slit lamp improves the image quality by magnifying the target tissue, the tradeoff is a smaller field of view. Therefore, it would be desirable to provide an instrument and method to better balance between the field of view seen and the quality of the viewed image.